Design, Development and Fabrication of Combustion chamber for Plasma Pyrolysis System

Abstract

Plasma pyrolysis is an emerging technology that can provide complete solution to organic solid waste disposal as well as it is possible to recover energy from variety of organic waste. In this technology plasma torch is used as a workhorse to convert electrical energy into heat energy. Ther- mal plasma provides extremely high temperature in oxygen free environment which is required for disintegration of waste in pyrolysis environment. The plasma pyrolysis system comprises of Power supply, plasma torch, primary (pyrolysis) chamber, secondary (combustion) chamber, Venturi & Secondary Scrubbers and induced draft fan. In this work, an attempt has been made to design an e cient combus- tion chamber to achieve better combustion e ciency. In the present work, polyethylene waste is pyrolysed in primary chamber with the help of plasma torch at a temperature greater than 2000 C in the plasma zone and greater than 600 C near the wall of primary chamber. On pyrolysis various gases such as CO, CH4, H2 and higher hydrocarbons along with some amount of soot particles are formed. These pyrolysed gases are combusted into car- bon dioxide and water vapour in the combustion chamber. As a result, the secondary chamber attains temperature 1000 C. The combustion chamber takes care of complete conversion of organic species which are formed in the primary chamber. Complete and e cient combustion is required to prevent the formation of toxic compounds such as dioxins and furans and soot par- ticles. If not designed properly, combustion chamber will release these toxic compounds in the environment which in turn will make the technology a polluting technology. In addition, calculations are also done for various factors that directly govern the combustion process and subsequently di erent changes have been made in the combustion chamber design. The 3T's i.e. turbulence, temper- v ature and residence time were adjusted by making appropriate changes in the design of the system. Later, several experiments were performed and e ciency of the modi ed secondary chamber was measured. The optimum conditions and design for obtaining better combustion e ciency in the exist- ing plasma pyrolysis system are described in the report. It has been found in this work that, better combustion e ciencies are achieved at combustion temperature 1000 C and residence time greater than 3.5 sec. In the conclusion, based on these results, parameters which should be taken into account while designing and fabricating e cient combustion chamber for plasma pyrolysis system have been discussed. In future there is a possibility of improving design of pyrolysis system as well as combustion chamber and making the system more useful for energy recovery as well as for safe disposal of waste for large variety of waste streams. This technology has great potential for safe disposal and recover energy from biomass, plastics, industrial waste, tyres and low calori c value coal.